During the past year we have proven the existence of a novel metal cluster containing 3 Fe atoms and labile sulfur. This center has been found in a ferredoxin from A. vinelandii, ferredoxin II from D. gigas, glutamate synthase from A. vinelandii, and aconitase, an enzyme isolated from beef heart. In the coming year we will continue to study these novel clusters. We will also continue our studies of extra- and intradiol cleaving dioxygenase enzymes. In particular, we will focus on the elucidation of the catalytic mechanism of extradiol cleaving enzymes (which cleave catechol rings adjacent to the two hydroxyl groups). Finally, we will continue our studies of hydrogenase, an enzyme which might play an important role in our future energy supplies.